froth

flotation

[floh-tey-shuhn]
or froth flotation

Most widely used process for extracting many minerals from their ores. The method separates and concentrates ores by altering their surfaces so that they are either repelled or attracted by water. Unwetted particles, which adhere to air that is bubbled through the water, will float in the froth, while wetted particles will sink. The process was developed on a commercial scale early in the 20th century to remove very fine mineral particles that formerly had gone to waste in gravity concentration plants. With its use to concentrate copper, lead, and zinc minerals, which commonly accompany one another in their ores, many complex ore mixtures formerly of little value have become major sources of certain metals.

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Froth is foam consisting of bubbles in a liquid.

One common form of froth is milk froth deliberately created as part of a drink. Many Italian-style coffees are made using a combination of espresso coffee, steamed milk and frothed milk. Most espresso machines have a steam pipe which is used to bubble steam through milk in order to froth it. This frothed milk is then poured on top of the drink.

In the United Kingdom, froth is also used to describe the layer of bubbles at the top of a glass of beer.

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